It could have gone undetected for three years until any of many possible things happened: maybe he dramatically increased his claim rate in 2019, causing software alarms to fire or a bureaucrat to notice; maybe an informant inside the business provided a tipoff; maybe a state or federal tax audit revealed he could not document the income; maybe USPS deployed updated or new fraud detection controls. Then after November 2019, they may have had to go to a grand jury, which was in recess for some of the holidays, and couldn't get an indictment until early January. Or none of these--people are innocent until proven guilty.
' Makes sense to me: if it (an insurance claim) worked once, why not do it again?
Lather, rinse, repeat.
What is interesting to me is the lack of an exit strategy, eg, you buy that house in the Caymans, not Miami, along with a small plane & flying lessons.
But, then, it has often been said that criminals do not commit crimes if they expect to be caught.
I do not know the total value of insurance claims against the USPS each year, but it would not take The World's Sharpest Auditor to figure-out that you ought to take a look at your biggest claimants once in a blue moon.